Low-temperature electron transport in Si with an MBE-grown Sb δ layer

Abstract

Studies of the electrical properties of Si single crystals with \ensuremath{\delta}(Sb) layers of various sheet densities ${N}_{D},$ of Sb atoms $(5\ifmmode\times\else\texttimes\fi{}{10}^{12}--3\ifmmode\times\else\texttimes\fi{}{10}^{14}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}2})$ have furnished detailed information about the low-temperature features of the electron transport in this system. The metal-type conductivity of \ensuremath{\delta} layers at ${N}_{D}>~3\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ exhibits manifestations of the weak localization of electrons and electron-electron interaction in a two-dimensional system. The temperature dependence of electron phase relaxation time, the spin-orbit interaction time, and parameter ${\ensuremath{\lambda}}^{D}$ of the electron-electron interaction are determined. It is found that a decrease in the electron density in the \ensuremath{\delta} layer is accompanied by decrease in the parameter ${\ensuremath{\lambda}}^{D}.$ The effect of electron heating by an electric field is used to find the temperature dependence of the electron-phonon relaxation time. At low temperature the hopping-type conductivity of \ensuremath{\delta} layers at ${N}_{D}<~1\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ is realized; at sufficiently low temperatures (10 K) the two-dimensional Mott law of variable-range hopping is seen. The nonlinearity of the current-voltage characteristics observed is well described by the theory of non-Ohmic hopping conductivity in moderately strong electric fields.